The present invention relates to a multiple parallel catalytic reactor assembly.
Before a catalyst is selected for use in a commercial application, a great number of known catalysts may be contemplated for use in the envisioned application. A large number of newly synthesized catalytic compositions may also be considered as candidates. It then becomes important to evaluate each of the potential catalysts to determine the formulations that are the most successful. in catalyzing the reaction of interest under a given set of reaction conditions.
Two key characteristics of a catalyst that are determinative of its success are the activity of that catalyst and the selectivity of the catalyst. The term xe2x80x9cactivityxe2x80x9d refers to the rate of conversion of reactants by a given amount of catalyst under specified conditions, and the term xe2x80x9cselectivityxe2x80x9d refers to the degree to which a given catalyst favors one reaction compared with another possible reaction, see, McGraw-Hill Concise Encyclopedia of Science and Technology, Parker, S. B., Ed. in Chief; McGraw-Hill: New York, 1984; p. 854.
The traditional approach to evaluating the activity and selectivity of new catalysts is a sequential one. When using a micro-reactor or pilot plant, each catalyst is independently tested at a set of specified conditions. Upon completion of the test at each of the set of specified conditions, the current catalyst is removed from the micro-reactor or pilot plant and the next catalyst is loaded. The testing is repeated on the freshly loaded catalyst. The process is repeated sequentially for each of the catalyst formulations. Overall, the process of testing all new catalyst formulations is a lengthy process at best.
Developments in combinatorial chemistry have first largely concentrated on the synthesis of chemical compounds. For example, U.S. Pat. Nos. 5,612,002 and 5766556 disclose a method and apparatus for multiple simultaneous synthesis of compounds. WO 97/30784-A1 discloses a microreactor for the synthesis of chemical compounds. Akporiaye, D. E.; Dahl, I. M.; Karlsson, A.; Wendelbo, R. Angew Chem. Int. Ed. 1998, 37, 609-611 disclose a combinatorial approach to the hydrothermal synthesis of zeolites, see also WO 98/36826. Other examples include U.S. Pat. Nos. 5,609,826, 5,792,431, 5,746,982, and 5,785,927, and WO 96/11878-A1.
Combinatorial approaches have been applied to catalyst testing to expedite the testing process. For example, WO 97/32208-A1 teaches placing different catalysts in a multicell holder. The reaction occurring in each cell of the holder is measured to determine the activity of the catalysts by observing the heat liberated or absorbed by the respective formulation during the course of the reaction, and/or analyzing the products or reactants. Thermal imaging had been used as part of other combinatorial approaches to catalyst testing, see Holzwarth, A.; Schmodt, H.; Maier, W. F. Angew. Chem. Int. Ed., 1998, 37, 2644-2647, and Bein, T. Angew. Chem. Int. Ed., 1999, 38, 323-326. Thermal imaging may be a tool to learn some semi-quantitative information regarding the activity of the catalyst, but it provides no indication as to the selectivity of the catalyst.
Some attempts to acquire information as to the reaction products in rapidthroughput catalyst testing are described in Senkam, S. M. Nature, July 1998, 384(23), 350-353, where laser-induced resonance-enhanced multiphoton ionization is used to analyze a gas flow from each of the fixed catalyst sites. Similarly, Cong, P.; Doolen, R. D.; Fan, Q.; Giaquinta, D. M.; Guan, S.; McFarland, E. W.; Poojary, D. M.; Self, K.; Turner, H. W.; Weinberg, W. H. Angew Chem. Int. Ed. 1999, 38, 484-488 teaches using a probe with concentric tubing for gas delivery/removal and sampling. Only the fixed bed of catalyst being tested is exposed to the reactant stream, with the excess reactants being removed via vacuum. The single fixed bed of catalyst being tested is heated and the gas mixture directly above the catalyst is sampled and sent to a mass spectrometer.
It is much more recent that combinatorial chemistry has been applied to evaluate the activity of catalysts. Some applications have focused on determining the relative activity of catalysts in a library see Klien, J.; Lehmann, C. W.; Schmidt, H.; Maier, W. F. Angew Chem. Int. Ed. 1998, 37, 3369-3372; Taylor, S. J.; Morken, J. P. Science, April 1998, 280(10), 267-270; and WO 99/34206-A1. Some applications have broadened the information sought to include the selectivity of catalysts. WO 99/19724-A1 discloses screening for activities and selectivities of catalyst libraries having addressable test sites by contacting potential catalysts at the test sites with reactant. streams forming product plumes. The product plumes are screened by passing a radiation beam of an energy level to promote photoions and photoelectrons which are detected by microelectrode collection. WO 98/07026-A1 discloses miniaturized reactors where the reaction mixture is analyzed during the reaction time using spectroscopic analysis. Some commercial processes have operated using multiple parallel reactors where the products of all the reactors are combined into a single product stream; see U.S. Pat. Nos. 5,304,354 and 5489726. U.S. Pat. No. 5,112,574 discloses an array of stoppers that may be inserted into the wells of any multititer plate.
Applicants have developed a multiple parallel reactor assembly to simultaneously test a plurality of catalysts in a rapid, economical, and consistent way. Applicants"" invention allows for easy simultaneous assembly of the multiple parallel reactors. The tops and bottoms forming the multiple parallel reaction chambers are attached to supports, one support for the plurality of tops and another support for the plurality of bottoms, so that assembly involves manipulating only the two supports instead of individually manipulating the significantly larger number of individual components. However, applicant""s invention retains a great deal of flexibility by not fully integrating the key components into the supports. Each key component is individually removable from the support. Worn or defective components are readily individually replaced without disturbance to other components. Similarly, the vessels containing the catalyst which are housed within the bottoms can be individually removed. The number of parallel reactors in the assembly is readily varied through the addition or subtraction of as little as one set of key components.
The purpose of the invention is to provide a multiple parallel catalytic reactor assembly having (1) a plurality of bottoms, each bottom having an open end and a closed end with the plurality being supported by a single first support; (2) a plurality of tops supported by a single second support with the plurality of tops engaged with the plurality of vessels to form a plurality of sealed independent reaction chambers; (3) a plurality of vessels for containing catalyst, each vessel having an open end and a fluid permeable end, and positioned within the reaction chambers so that the open ends of the vessels are in alignment with the open ends of the bottoms (4) a plurality of first fluid conduits in fluid communication with the reaction chambers, and (5) a plurality of second fluid conduits in fluid communication with the reaction chambers. A specific embodiment of the invention is one where one or more heaters are positioned adjacent the plurality of bottoms to heat the bottoms and the reaction chambers. Another specific embodiment of the invention is one where one or more seals are used to engage the plurality of bottoms and the corresponding plurality of tops and optionally another seal or seals to engage the plurality of vessels and the plurality of tops to form the sealed reaction chambers.
Another purpose of the invention is to provide a process for conducting multiple parallel catalyst evaluations using the multiple parallel catalytic reactor assembly described above with the advantage of simultaneously sealing all the open ends of the plurality of bottoms with the plurality of corresponding tops to form the multiple sealed independent reaction chambers. A specific embodiment of the invention also includes simultaneously opening all the multiple sealed reaction chambers by removing the plurality of tops from the open ends of the lurality of bottoms. Another specific embodiment of the invention is one where the plurality of vessels containing catalyst are removed from the plurality of bottoms.